Bumper repair tools and process of manufacture

ABSTRACT

This application discloses a mold for making die sets for bumper repair, a method of making the mold, and a method of making the dies. The mold is made from an undamaged bumper section to which extensions are added to make an enclosure suitable for simultaneously casting both of the male and female die members. The welding and a subsequent step of heat treating is accomplished in such a way that the longitudinal curvature is greater than that of the original bumper so that the resulting die set tends to overbend bumpers being repaired. The mold is placed in a flask with side walls and liquid casting metal is introduced inside and outside of the mold, filling the inside and substantially enclosing the outside. After hardening, the flask and mold are removed, leaving a matching, fully congruent die set. The working (pressing) surfaces of the die thus obtained correspond exactly to each other and are true copies of the faultless original bumper segment, except for the added curvature.

United States Patent 1 1 Lang Aug. 21, 1973 BUMPER REPAIR TOOLS AND PROCESS OF MANUFACTURE [76] Inventor: lmre Lang, Santa Barbara,

Willowdale, Toronto, Canada [22] Filed: June 11, 1971 [21] Appl. No.: 152,273

Related US. Application Data [63] Continuation-in-part of Ser. No. 870,468, Oct. 22,

1969, abandoned.

[52] U.S. Cl. 72/475, 72/702, 72/705 [51] 821d 37/14 [58] Field of Search 72/352, 475, 375, 72/414, 470, 705, 476

[56] References Cited UNITED STATES PATENTS 3,442,663 1/1969 James et al. 72/476 3,459,018 8/1969 Miller 72/702 266,653 10/1882 Spaulding 72/352 2,255,987 9/1941 Schultz 72/705 1,680,467 8/1928 Matheson 72/375 3,036,623 5/1962 Hanak 72/705 3,066,719 12/1962 Selnick 72/705 OTHER PUBLICATIONS Van Der Burgt, Die Modifications Control Springback in Bending, Tool & Manufacturing Engineer;

Vol. 61, No. 4, Oct. 1968.

Primary ExaminerCharles W. Lanham Assistant Examiner-M. J. Keenan Attorney-Roylance et al.

[5 7] ABSTRACT This application discloses a mold for making die sets for bumper repair, a method of making the mold, and a method of making the dies. The mold is made from an undamaged bumper section to which extensions are added to make an enclosure suitable for simultaneously casting both of the male and female die members. The welding and a subsequent step of heat treating is accomplished in such a way that the longitudinal curvature is greater than that of the original bumper so that the resulting die set tends to overbend bumpers being repaired.

The mold is placed in a flask with side walls and liquid casting metal is introduced inside and outside of the mold, filling the inside and substantially enclosing the outside. After hardening, the flask and mold are removed, leaving a matching, fully congruent die set. The working (pressing) surfaces of the die thus obtained correspond exactly to each other and are true copies of the faultless original bumper segment, except for the added curvature.

1 Claim; 9 Drawing Figures lllllllir PIHENTEB 3.753.368

mm or 2 FIG. I

FIG. 4

= INVENTOR l9 IMRE LANG BY QAMM/ gyw'zj ATTORNEYS PAIBIIED 3.753.368

SHEEI 2 Bf 2 FIG. 7

IN VENTOR IMRE LANG ATTORNEYS:

FIG. 9

BUMPER REPAIR TOOLS ANDPROCESS OF MANUFACTURE This application is a continuation in part of U. S.'Pat. application Ser. No. 870,468, filed Oct. 22,1969, now abandoned.

This invention relates to dies for use in the repair of automobile bumpers, to a-method of making such dies, to the molds for making the dies, andto a method of making the molds.

It has traditionally been common practice to repair damaged bumpers byihammering them into a shape approximatelytheir original shape. This technique istiresome and time consuming, andthe result'is not satisfactory, especially with bumpers of recent-design in which complex curvatures cannot be restored by manual pounding.

A more recent technique is to use a'press, usually hydraulically powered, in which the bumper to be repaired is pressed between amoving portion, referred to and resembling a blade, and a fixed portion, called the plate, cross bars or anvil. The blade is attached to the moving shaft of the press and caused to repeatedly approach the anvil and squeeze dents and distortions from the bumper while the position of the bumper on the anvil is repeatedly readjusted. This is, of course, simply a power-driven improvement on the manual hammering approach, and suffers from similar disadvantages, especially in that the resulting repaired bumper is not at all like a new one because the curves cannot be smoothly restored by the blade press technique.

It has been found that a quick and economical job can be done, and good quality results obtained, with the use of properly shaped press tools which are produced from, and are shaped like, the original, undistorted and undamaged bumper.

It was recognized that the most desirable repair tool would include dies somewhat like those originally used to produce the bumpers. However, these production dies are designed and constructed to form a bumper from a substantially flat metal sheet. Accordingly, they are made of steel and are formed by the use of expensive precision tool and die making techniques.

-It is necessary for a bumper repair shop to maintain the ability to repair bumpers for nearly any model of automobile for at least a few model years.

Quite clearly, it would be prohibitively expensive for a bumper repair shop to obtain and stock dies of that type for each bumper style to be repaired; and, in addition, it is believed that such dies would not have certain design features, to be described'hereinafter, which are important to successful bumper repair.

In accordance with the present invention, male and female dies, having the configuration of the bumper to be repaired, are simultaneously produced by using a mold which is produced from an undamaged bumper, modified to create the necessary walls, etc. needed in a mold.

In one aspect of the invention, the mold is produced by adding to a bumper, or a section thereof, walls constituting continuations of the rearwardly extending walls of the original bumper, and also walls to close cut-out portions of the bumper such as those provided for turn signal or parking lamps, openings to the radiator, etc. The added walls are welded to the existing bumper segment in such a way as to increase the female die portions can be made simultaneously from the same mold, in the same flash, under identical conditions of temperature and other physical conditions, by a single casting operation, so that the mating portions of the dies mate exactly. The die portions are cast using a metal of relatively low melting point such as a conventional zinc alloy casting metal.

In order that the manner in which the foregoing is achieved in accordance with the invention can be understood in detail, preferred embodiments thereof will be described with reference to the accompanying drawings, which form a part of this specification, and wherein:

FIGS. 1 and 2 are plan views of typical rather simple bumpers to be used for making molds and dies;

FIG. 3 is a side elevation of a flask and mold to be used for die making;

FIG. 4 is a plan view of the flask and mold of FIG. 3; FIG. 5 is a vertical section along lines 5-5 of FIG.

FIG. 6 is an exploded end view of the dies and a bumper section in position for use;

FIG. 7 is a perspective of a mold formed from a bumper section; and

FIGS. 8 and 9 are partial sections of the bumper and mold of FIG. 7.

The manner in which the mold is made will be described first. Although a mold could be made for the entire bumper, it is much better to make separate molds (and separate sets of dies) for segments of the bumper, primarily because of the great size and weight that a single die for the entire bumper would involve. Generally, three segments are used, although from two to five or more are sometimes made for bumpers having unusuallly simple or unusually complex shapes.

For purposes of the present discussion, bumpers of relatively simple shapes will be used. In FIGS. 1 and 2 are shown two identical bumpers A and B in plan, i.e., as they would be viewed from above when mounted on an automobile. These bumpers are cut along the solid lines 21, 22, 23, 24 to form pattern sections 1, 3 and 5. It will be observed that the short segments between the solid and dotted lines at the ends of the pattern sections constitute intentional overlap, i.e., they duplicate a small portion of the adjacent pattern section. Those sections identified as 2, 4 and 6 are unusable and are discarded.

Molds are produced from the pattern sections by welding wall portions to each section as shown in FIG. 7, which illustrates this aspect of the invention using a bumper portion of a different shape. In FIG. 7 is shown a bumper section, indicated generally at 25, having an upper rail 26 and a lower rail 27. Between those two rails is a space through which air can pass to the radiator when the bumper is mounted on an automobile. To make the section into a mold, this space is closed by welding side walls 28 and an end wall 29 to the trailing inner edges 30, 31 of the rails and to each other, thus forming a box. Holes 32 are provided to let air escape when the mold is filled. An end plate 33 is also provided. Further wall 34, 35 are welded to the trailing exterior edges 36, 37 of the bumper so that a container having an open top defined by the distal edges of walls 32 and 33, and having a bottom defined by the bumper section itself and the interior box, is formed.

The exterior surface of the mold formed as described above will, in the casting process, create the inner surface of the female die member. Thus, it will be seen that the exterior of the joint at, for example, edge 36, cannot have any protrusions and must be formed or ground smooth.

It will also be recognized that some bumpers are formed with a tuned-in lip, such as that shown in FIG. 8, edge 37 of the bumper in FIG. 7 being used for purposes of this example. In that event, the mold is formed by making a double wall at the section shown as illustrated in FIG. 9, with a first external wall 39 being welded at the outer portion of edge 37 and a second wall 41 being welded to form the inner surface which is then smooth and uninterrupted to the deepest part of the mold.

Turning now to the casting process, it will be seen in FIGS. 3-5 that the pattern section 5 has been provided with extension walls 7 and 8 which are substantially the same as walls 34 and 35 discussed with reference to FIG. 7. These walls are welded to the bumper along weld lines 7A and 8A and the bumper section with its extension walls is welded to and suspended between end plates 11 and 12. It will be observed that the end plates extend below the bottom of the lowermost portion of the bumper, permitting that portion to be spaced from a supporting or base plate 15 to permit the female mold to be formed therebetween, the actual spacing being determined by the desired thickness of the resulting die.

Side walls 9 and 10 connect the end walls and provide a gap at the upper edges of the mold and the side walls to allow the castingmetal to flow therebetween. The mold thus formed is placed in a flask 13 which can be packed with sand in the spaced indicated at 16. The flask can also be provided with suitable cooling means in base plate 15 to cause the center portion of the die to cool and harden earlier than the remainder thereof so that additional material can be supplied at the upper edges to prevent the possible formation of voids in the dies.

During the casting process, molten casting metal is poured into the space indicated generally at 14, which material flows into the void between base plate 15 and the bottom of pattern section 5, forming the female portion of the die. The mold can be maintained in a heated condition to prevent premature hardening of the casting material by applying the flame of a torch thereto while the metal is being poured in. Thereafter, the interior of the mold is filled with casting material to form the male portion of the die.

While the male portion of the die is still in a liquid state, a holding member 17 such as an externally threaded shaft, or a plurality of such members, can be dipped into the upper portion of the male die and suspended in that position until the die hardens, thereby trapping the holding member therein. In use, as illustrated in FIG. 6, a supporting plate 18 is attached to the male die, this plate being of thick rigidmaterial such as a plate of st'eel'about 2 inches thick. This is firmly attached to the die to provide the necessary structural strength which is inherently not present in the zinc casting material. Member'17, or its equivalent, is then attached to the moveable shaft of a pressing machine and the lower die portion, 19, is attached to the anvil or plate of the press. A damaged bumper such as 20 can then be placed between the two die portions and, in a single motion, the die portionscan be brought together pressing the bumper therebetween and removing all such dents and distortions.

A feature which contributes to the successfulness of the above described process and which has been mentioned before but not fully described involves the additional curvature which is supplied in manufacturing the mold and which, accordingly, results in the dies produced from the mold. This curvature is introduced along the longitudinal axis of the bumper section at the time the mold is made. The longitudinal axis to which reference is made is illustrated in FIG. 2 as the axis 40. When side plates 7 and 8 are added to the trailing edges of the bumper to produce the mold therefrom, or when wall 34 is added to the bumper shown in FIG. 7, the weld produced at the junction line between the bumper and the added material tends to shrink when it is cooled. By appropriately heat-treating the added plate during and after the weld is produced, the plate can be caused to shrink and to absorb some of the stress produced by the weld, with the result that the plate is of smaller dimension, and has a more curved weld edge, than when it was originally attached to the trailing edge of the bumper. This introduces an additional curvature into the bumper itself along the axis generally indicated at 40.

The appropriate heat-treating mentioned above constitutes relieving the stresses in the plate by heating the plate with the welding torch in a relatively uniform fashion and then hammering the plate beginning with the portions near the weld and at the ends of the mold section, and working toward the center portion of the plate at a point furthest from the weld. This heating and hammering process results in effectively diminishing the overall size of the plate to the point where the curvature is permitted. It will be recognized by those skilled in the metal working arts that a solid and flat anvil surface behind the plate is essential during the heating and hammering process.

While various embodiments have been described it will be recognized that variations will appear to those skilled in the art from this disclosure, and that such variations reside within the invention asdefined in the appended claims.

What is claimed is:

l. A die set for repairing automobile bumpers of a specific preselected design comprising first and second mating die portions simultaneously cast from a low melting point metal in a single mold comprising an undamaged bumper portion of the same specific design, said bumper portion having a longitudinal axis, said die portions being precisely matched to each other and having cooperating mating surfaces with shapes corresponding to respective inner and outer surfaces of the undamaged portion and a longitudinal curvature along said axis which exceeds the curvature of the original undamaged bumper of the same type so that a bumper being repaired is overbent and allowed to spring back when a damaged bumper section is sequentially compressed and released between the die portions.

II k 1' k 

1. A die set for repairing automobile bumpers of a specific preselected design comprising first and second mating die portions simultaneously cast from a low melting point metal in a single mold comprising an undamaged bumper portion of the same specific design, said bumper portion having a longitudinal axis, said die portions being precisely matched to each other and having cooperating mating surfaces with shapes corresponding to respective inner and outer surfaces of the undamaged portion and a longitudinal curvature along said axis which exceeds the curvature of the original undamaged bumper of the same type so that a bumper being repaired is overbent and allowed to spring back when a damaged bumper section is sequentially compressed and released between the die portions. 